When performing a laser marking operation with respect to a thin wafer or a wafer having a warpage, the wafer is likely to be damaged. Therefore, to avoid damaging the wafer, a method of performing a laser processing operation in a state where a processing tape is attached to a surface of the wafer has been used. In this case, in order to perform the laser marking operation with respect to the wafer to which the processing tape is attached, a laser beam needs to be irradiated through the processing tape to reach the surface of the wafer. In general, the processing tape attached to the wafer may be formed of various materials, and thus, a transmittance of the laser beam through the processing tape may vary depending on the material of the processing tape. The quality of the laser marking operation with respect to the surface of wafer is dependent upon the transmittance of the processing tape.